The comparative analysis of masticatory muscles electromyographic activity in patients with orthodontic disorders and those with orthognatic bite

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УДК616.314-089.23-06:611.732.7-073.7 DOI 10.11603/2311-9624.2016.3.6854

©Yu. M. Martits, I. R. Plavutska

I. Horbachevsky Ternopil State Medical University V. Hnatiuk Ternopil National Pedagogical University

The comparative analysis of masticatory muscles electromyographic

activity in patients with orthodontic disorders and those with

orthognatic bite

Summary. The analysis of bioelectric activity of masticatory muscles, as well as such characteristics as their symmetry and synergy is recommended to determine the degree of functional disorders of these muscles. The objective: to conduct a comparative analysis of electromyographic activity of masticatory muscles in patients with orthodontic disorders and those with orthognatic bite. The materials and methods: a total superfi cial electromyography of m. Masseter and the front part of the m. Temporalis in 87 people with the presence of orthodontic pathology and 22 persons with orthognatic bite at compression on teeth and cotton rolls. The re-sults: it is determined the reduction of the average amplitude parameter of the same name muscles and ratio indexes of the average amplitude of the muscles of the right and left side at compression on rolls compared to the compression on teeth in both observed groups. Statistically signifi cant differences form. Masseter were not found when comparing the coeffi cient of the same name muscles coordination between the groups, as op-posed to the following measures for m. Temporalis (p<0,05). Conclusion: The condition of occlusion appears on the EMG results, which have been confi rmed by us in this study. At orthodontic pathology the EMG results should be evaluated together with the results of other studies (the diagnostics of TMD, clinical functional analysis, TMJ study). It is necessary to conduct further research in this area in order to highlight and explain some causes of the appearance of masticatory muscles asymmetry, its connection with orthodontic pathology, its impact on the course of the disease and the results of orthodontic treatment.

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Ключові слова: ортодонтична патологія, ортогнатичний прикус, поверхнева електроміографія, жу-вальні м’язи, симетрія, синергія.

Ю. Н. Мартиц, И. Р. Плавуцкая

ГВУЗ «Тернопольский государственный медицинский университет имени И. Я. Горбачевского» Тернопольский национальный педагогический университет имени Владимира Гнатюка

Сравнительный анализ электромиографической активности

жевательных мышц у лиц с ортодонтической патологией и лиц с

ортогнатическим прикусом

Резюме. Анализ показателей биоэлектрической активности жевательных мышц, а также та-ких характеристик, как их симметричность и синергизм рекомендуют для определения степени функциональных нарушений указанных мышц. Целью исследования было провести сравнительный анализ электромиографической активности жевательных мышц у лиц с ортодонтической патологи-ей и лиц с ортогнатическим прикусом. Проведено поверхностную суммарную электромиографию m. Masseter и передней части m. Temporalis у 87 лиц с наличием ортодонтической патологии и у 22 лиц с ортогнатическим прикусом при сжатии на зубах и на ватных валиках. Определено уменьшение среднего показателя амплитуды одноимённых мышц и индексов соотношения средних показателей амплитуды мышц правой и левой сторон при сжатии на валиках в сравнении со сжатием на зубах в обеих группах наблюдения. При сравнении коэффициента координации одноимённых мышц между группами статистически значимых отличий для m. Masseter не выявлено, в отличие от тех же пока-зателей для m. Temporalis (p<0,05). Состояние окклюзии отражается на результатах ЭМГ, что было под-тверждено нами в данном исследовании. При наличии ортодонтической патологии результаты ЭМГ нужно оценивать в комплексе с результатами других исследований (диагностика дисфункций ВНЧС, клинический функциональный анализ, исследование состояния ВНЧС). Необходимо проводить даль-нейшие исследования в этом направлении с целью выделения и выяснения отдельных причин воз-никновения асимметрии жевательных мышц, её связи с наличием ортодонтической патологии и влияния на течение и результаты ортодонтического лечения. Ключевые слова: ортодонтическая патология, ортогнатический прикус, поверхностная электромиография, жевательные мышцы, симметрия, синергия.

Introduction. Occlusion pathology is associated

with disorders of the temporomandibular joint (TMJ) and changes of the masticatory muscles functionality [2, 8]. During the study when creating experimental occlusal interferences asymmetrical jaw muscles-elevators contraction occurred, but there were no symptoms of tempo-ro-mandibular disorder (TMD) [8]. Based on these data, it was concluded that asymmetric activation of the masticatory muscles, found in the pathology of occlusion, deformation and adentia and in dysfunctional states of TMJ is a compensatory mechanism for achieving the stability of the lower jaw during chewing [9, 11].

To characterize the functional state of masti-catory muscles according to the results of elec-tromyography (EMG) it was proposed functional tests, the main of which was the rest position and maximum willful compression (MWC). In many studies [4, 9, 13] it was proved that the rate of the MWC depends on the number of occlusal contacts

and their location on teeth, bite height and the presence of pathology bite.

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not determine statistically signifi cant differences between the groups (p>0,05). The analysis of study results according to the algorithm of total superfi cial EMG showed signifi cant differences between the rates of temporal and masticatory muscles, which once again confi rmed the impact of a number of general and local factors, including the patient’s condition and technical characteristics of the electromyograph, on the results of the study [3, 4, 10].

During the qualitative analysis of total superfi cial EMG it was found that bursts of spontaneous activity at rest position were observed in 38.2 % of the working group, while the control group included 4.2 % of the patients. The activity of masticatory muscles in rest position in the patients of the control group was within the established norm (less than 2 % of the index MWC) [10]. In 7 patients (8.1 %) of the working group overall level of activity slightly exceeded the allowed norm and was defi ned as 2.16–3.03 mcV. Several people in both groups at MWC with cotton rolls and without them demonstrated the predominance of m. Temporalis over m. Masseter: 4 people in the experimental group (4.6 %) and 1 person in the control group (4.5 %). The parameters of m. Masseter amplitude prevail in most patients examined according to the results of MWC. BEA index m. Masseter at maximum willful compression in central occlusion is an individual indicator and data presented in various literary sources differ signifi cantly. According to the statement [7], the increasing of the activity of m. Masseter indicates chronic bruxism or lowering the bite height. Reducing the height of the bite, which is observed in particular in orthodontic pathology II class by Angle, is often accompanied by a BEA decrease of chewing muscles. Their asymmetry at closing may occur due to disharmony of occlusal ratios of left and right side dentition. M. Masseter and m. Temporalis react differently to changes in occlusal correlations that may affect the stability of the mandible at compression [9].

The comparison of EMG studies according to the amplitude parameters of the same name muscles at compression in the control group identifi ed its reduction at compression on rollers at an average of 1/3 compared to the compression on teeth, but without statistically signifi cant differences in the t-test (p>0.05 ). Indicators m. Masseter were signifi cantly different in each person, average parameters were determined with great errors and deviations, indicated by the fi gures of Maximum (Max) and minimum (Min) (Table 1).

pathology bite, and hence a detailed study of these indicators is important in dentistry.

The objective of the study. Comparative analysis of masticatory muscles electromyographic activity in patients with orthodontic disorders and those with orthognatic bite.

Materials and methods. For the study

it was selected 87 individuals (41 male and 46 female) with the presence of orthodontic pathology among the students of Dental Faculty of I. Horbachevsky Ternopil State Medical University. The average age of the patients was 19.3 + 1.1 years. The criteria for inclusion were the patient’s consent for the survey, the lack of medium and large defects of dentition, without signs of acute temporo-mandibular disorder. The study excluded people with medium and large defects of dentition, severe tooth-jaw deformities, as well as tooth decay and its complications, generalized periodontitis in the acute stage. To control during this study it was selected a group of 22 people with orthognathic bite, with no signs of muscle-joint dysfunction and periodontal disease (average age – 19.2 + 0.9 years). These individuals were examined by the standard scheme of history case with clinical functional analysis. We conducted electromyographic study using electromyograph BioEMG III of BioPack complex according to the manufacturer’s recommendations (Bio RESEARCH Assoc. Inc., USA). The analysis of bioelectric activity of masticatory muscles (front m. Temporalis, superﬁ cial part of the m. Masseter) at rest position and at MWC for 5 seconds was conducted. We determined the symmetry, the average amplitude and synergy of the various groups of masticatory muscles when performing this function. The study was repeated using cotton rolls placed on molars. Comparative analysis of the teeth compression results and those using rolls in lateral areas of the jaws was performed for each series and it was determined the balance of symmetric masticatory muscles on the left and on the right at a coordination rate of bioelectrical activity (BEA) by Aav., which provides correlation miscalculation of the same name muscles [3, 6]. The level of chewing muscles asymmetry was also determined according to the method [10], where the difference between the higher and lower index of similar amplitude of the same name muscles was divided by the maximum amplitude and multiplied by 100%. Survey results were analyzed using statistical package NCSS 2007 software (V. 07.1.20, Utah, USA).

The results and discussion. The comparative

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In the working group the results of EMG studies according to the amplitude parameters of the same name muscles at compression were as follows. It was revealed the decrease of an average activity at compression on rollers to an average of 1/3relatively to compression on teeth, but there were no statistically signiﬁ cant differences in the t-test (p>0.05). Average parameters were determined with great errors and deviations, with signiﬁ cant differences of values «Max» and «MIN» (Table 2).

While analyzing the amplitude of MWC of masticatory muscles some peculiarities were discovered. In the control group 1 person (4.5 %)

demonstrated an increased activity at compression on cotton rolls compared to compression with no rolls (83.1 mcV and 58.8 mcV, respectively) m. Masseter on the left. While other examined patients in this group showed the decrease of the amplitude at biting on cotton rolls compared to the compression with no rolls. Processing the data received in the working group it was found the increase of amplitude in the right m. Masseter at compression on rolls (44 patients or 50.6 %), while the value of this increase amounted to 1.5 to 22.7 mcV. In the left m. Masseter 26 individuals (29.9 %) showed changes from 1.9 to 35.6 mcV.

Muscles mtype of loading

Indicators of amplitude BEA of masticatory muscles, mcV

Max–Min

m. Masseter (right) Without cotton rolls 51.18+6.37 116.72–21.53

With cotton rolls 35.07+5.48 79.26–18.44

m. Masseter (left) Without cotton rolls 79.43+15.68 238.54–24.71

m. Temporalis (right) Without cotton rolls 42.16+7.05 90.72–18.37

m. Temporalis (left) Without cotton rolls 41.21+7.37 113.59–21.74

Table 1. Comparative analysis of the average amplitude of muscles lifts the lower jaw

in the control group (n=22), p>0.05

In m. Masseter on the right similar changes were found in 15 (17.2 %) patients and the magnitude of such changes ranged from 2,6 mcV to 23.1 mcV, in m. Temporalis on the left - in 26 people (29.9 %) at a value of 2.4 mcV to 32.5 mcV. In general, changes towards increasing of the compression amplitude were typical for patients with reduced height of bite (distal occlusion or second class by Angle). According to some authors [1, 4] this symptom is

considered to be the factor that provokes TMD. The comparison of the highest or average activity in percentage is mostly used to assess the symmetry violation. The presence of asymmetry in the masticatory muscles functioning is a warning sign. It is believed that it precedes the occurrence of TMD. That is why we conducted the analysis of symmetry of chewing muscles BEA at the MWC on teeth and using cotton rolls. The study identiﬁ ed

Muscles Type of loading

Indicators of amplitude BEA of masticatory muscles, mcV

Max–Min

m. Masseter (right) Without cotton rolls 58.37+5.25 127.43–2.58

m. Masseter (left) Without cotton rolls 74.23+7.52 216.02–8.58

With cotton rolls 54.63+8.49 194,81–9.64

m. Temporalis (right) without cotton rolls 32.76+2.37 69.57–8.28

m. Temporalis (left) Without cotton rolls 35.37+2.48 63.35–8.39

Table 2. Comparative analysis of the average amplitude of muscles lifts the lower jaw

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a slight reduction of average indexes ratio of the muscles on the left and right sides at compression on rolls compared with compression on teeth, but without statistical authenticity (p>0.05). The index of coordination BEA m. Masseter and m. Temporalis(Aav.) was calculated. According to the data of literary sources for this parameter results no less than 87.0±0.9 % is considered to be physiological [6]. As a result of our research in most cases of Aav. we obtained more than 100% (124±12 % 117±15 % 122±17 %), indicating a signiﬁ cant prevalence of EMG amplitude parameters on the left. Statistically signiﬁ cant differences between the coordination indexes at teeth compression and compression on rolls was not found (p>0.05) (Table 3).

According to the recommendations [10] we determined asymmetry coeﬃ cient of ratios m. Masseter on the left and right sides. In the control group, the rate at compression on the teeth was

26.1±3 %, using cotton rolls – 26.8±6 %. For m. Temporalis this ﬁ gure in this group was 31.8±5 % at compression on teeth and 35.2±6 % at compression on rolls.

No signifi cant statistical differences when comparing the indexes of the asymmetry ratios for m. Masseter and m. Temporalis at compression on teeth and the one on rolls were found. This resulting average coeffi cient of asymmetry for m. Masseter was signifi cantly lower (t-criterion, p>0.05).

Within a working group calculated index of asymmetry for m. Masseter at compression on teeth was 27.6±6%, the one on rolls – 28.2±1 %. The same ﬁ gure for m. Temporalis was 15.8±4 % and + 21.4 % respectively. Statistically signiﬁ cant differences were found when comparing the indices for m. Masseter and between indexes of m. Masseter and m. Temporalis at compression on teeth and on rolls.

control group

(n=22) working group(n=87) t p

m. Masseter Without cotton rolls 1.35+0.16 1.48+0.17 0.72 p>0.05

With cotton rolls 1.28+0.18 0.96+0.08 1.61 p>0.05

m. Temporalis Without cotton rolls 1.52+0.12 1.61+0.13 0.51 p>0.05

With cotton rolls 1.05+0.17 0.59+0.11 1.28 p>0.05

Table 3. A comparative analysis of the average rate of muscle coordination

By analyzing the ratio of asymmetry for m. Masseter and m. Temporalis at compression on teeth we found a signifi cant difference (t2-Student’s criterion = 2.84, p2<0.05). When analyzing correlations of asymmetry indices for m. Masseter and m. Temporalis at compression on rollers marginal difference (t3 = 1.87 at t-critical = 2.012, p3≥0,05) was found. We found no statistically signifi cant differences between the degree of asymmetry for m. Masseter at compression on teeth and rolls when comparing the parameters in the control and working group. At the same time, statistically signifi cant differences between the working and control group were found while comparing the asymmetry for m. Temporalis (t1, p1 – Table 4).

According to studies [10], the asymmetry at the level of 10–15 % is already signiﬁ cant for m. Masseter. This phenomenon was observed in both groups approximately equally and demonstrated with asynchrony in the MWC early phase.

In most studies in Ukraine, much attention is paid to the prevalence of asymmetry of masticatory muscles at closing and chewing in patients with TMD [2, 5, 6], while the presence of orthodontic

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Conclusion. The condition of occlusion appears

on the EMG results, which have been conﬁ rmed by us in this study.

At orthodontic pathology the EMG results should be evaluated together with the results of other studies (the diagnostics of TMD, clinical functional analysis, TMJ study). It is necessary to conduct further research in this area in order to highlight and explain some causes of the appearance of masticatory muscles asymmetry, its connection with orthodontic pathology, its impact on the course of the disease and the results of orthodontic treatment. It should be also noted, that the analysis of the maxillofacial muscles-synergists signiﬁ cantly enhances the evaluation of the results.

It is necessary to conduct further studies to determine changes of amplitude and asymmetry parameters when performing functional tests during electromyography, because jaw closing is a complex process, and it can be infl uenced by the existing occlusal contacts. It should be clearly understood that a number of factors as occlusal, joint and neuromuscular ones can affect the fi nal result of orthodontic treatment and therefore the received fi ndings should be interpreted with caution.

It is necessary to investigate in greater detail the tests when placing jaws on cotton rollers to determine the indications for their use. The matter of asymmetry occurrence and connection of the given parameter with the presence and severity of orthodontic pathology requires further study. Control group

(n=22) Working group(n=87) t1 p1

m. Masseter Without cotton rolls 25.4+4 27.3+2 0.37 p>0.05

With cotton rolls 25.1+3 27.8+3 0.52 p>0.05

m. Temporalis Without cotton rolls 34.3+5 17.3+3 2.58 p<0.05

With cotton rolls 38.6+3 22.8+2 2.98 p<0.05

Table 4. A comparative analysis of similar muscle asymmetry coeﬃ cient

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